AA 642 then UA 638 at O'Hare
Dallas-Fort Worth → Chicago → San Francisco
Timetable, Chicago time
13:10AA 642 from Dallas-Fort Worth at the gate
12:42UA 638 to San Francisco leaves the gate
23 h 32 apart on the timetable, overnight
UA 638 leaves 23 h 32 after AA 642 arrives on the timetable: more than half a day, so not a connection we count.